Electrical circuits



Nov. 23 1926.

H. NYQUIST ELECTRICAL vCIRCUITS Filed Sept 6 l 1924 /Vo Eef/ecf/on L I l um I nu A TTORNEY Patented Nov. 23, 1926.

- 1,607,687 ."UNITED STATES PATENT OFFICE.

. EARTH-Y NYQUIST, OF JACKSON HEIGHTS, NEW YORK, ASSIGNOR TO AMERICAN TELE- PHONE AND TELEGRAPH COMPANY, CORPORATION 0I' NEW YORK.

, ELECTRICAL lCIRCUITS.

p Application filed September 6, 1924. Serial No. 736,378.

The object of my invention is to provide a new and improved method for economiz ing in the use of apparatus to produce desired changes in electric currents Anotherobject'of my invention is to provide apparatus for modifying an electric current 1n a desired manner with eii'ective use of the elements of the apparatus. Another object of my invention relates to reducing the amount of apparatus in an electrical network by employing reflection and utilizing the same network for transmission two ways.`

These and various other. objects of my-invention will become apparent on consideration of a specific example which I have chosen for disclosurein the following speci` g fication and claims takenwith the accomtion to be defined' in the claims.

panying drawings. that the following specification relates to this example of the invention, leaving the inven Referring. to the drawings, Figure 1 is a diagram illustrating a two-way wire and wireless transmission system in Vwhich my invention finds useful application; Fig. 2 is a diagram of a delay circuit that may be employed in the .system of Fig. 1; and Fig. 3 is a diagram of a delay circuit embodying my invention.

In the system shown in Fig. 1, 1V, and

Elare-two telephone stations, each with a` transmitter and receiver, and the apparatus lying between these stations is adapted to transmit-speech both ways, partl by wire and partly by wireless. The normal condi tion of the system when not in use involves a closure off the shunt 21 at the back contact ot' the amplifier-detector 'unit relay lA2.'

When El speaks, the transmission is into the .hybrid coil H2 which connects with a fourwire line, as shown. Thenge the voice currents go through repeatersRvandover-the wire line L,L to theradio transmitter T2 from which the radio Waves are, received by the radio receiver Rc1. Thence transmission is over the line L2 throughthe repeatersR to the hybrid coil H1 andltlience to the station W1. 4

The transmission, as thus described, is not affected by the shunt 22, because it is open at the front contact of the relay system A2. The symbol A1 indicates an amplil Iier-detectorfunit relay which isyoperated by thevoieeeurrent in the line L2 and, while 'the voic'elcurrent-s are being carried from It will be understood st'tionl E1 to station W1, the relay A1 is energized and closes on its front contact the shunt 23, thus inhibiting transmissionA from If the subscriber at W1 speakswhile the system is not in use, the voice currents in the primary windings of the hybrid coil H1 will occasion voice currents in. the line L1 and repeaters R which will go to the ampli- {ier-detector unit relay A2 and open the shunt 2l and close ftheshunt 22. The open* ing of the shunt 21 will make the system operative for transmission from W1 to E1, and the closing of the shunt 22 will make it inoperative for transmission vthe vother Way.-

In order that the transmission-from W1' to E, may not be mutilated, the delay circuit D is interposed. This is so arranged `that, while the initial voice current Waves are passing through D on the way from W1 to E1, the relay An will have time to oper-v ate so that when these waves reach the output of DA the shunt 21 will have been opened, and they will pass in unmutilate'd condition tion YV, and thence'in an the subscriber at E1.

It willbe seen that, although the system is a four-wire system, it is so arrangedat station W that -onl one pair` isoperative at onetime. Norma ly the painfrom E1 to `W1 -will be operative in virtfue of the normallynopen condition of the'shunt 22, and

the pair fromV1 to'E1 will be inoperative y on over theline L1 to the transmitting staobvious manner to because of the closure of the shunt 21.

`When El talks, then as ,long ashe talks continuously he `sust-ains this condition by Avirtue of the energization of relay A1 which closes the shunt 23 and prevents energizing relayA2 Whichwould close the shunt 22.

l/V1 'can' get possession of the line only when E, is nottalking and when, accordingly, the

relay'A1 is not energized.` Then when. Wl'* neen scribed thus for, there is no current to ted wave would have been.

in 2. consists of a large number et series coils L and alternately disposed shunt condensei's C, the terminal' condensers having' appropriate capacity values Adiffering :trom the others as indicated by the character @1. lo get the necessary delay., the number of sections in the network of Fig. 2 may l be as great as several hundredi' To reduce the "quantity of apparatus inyolyed, l constructthe network l) in accordance with Fig. 3, instead ot Figui The voice eurrents"`coming in from the lett to the terminals 24 divide equally, half going to' t le network N and half to the network so that there is a balance in the secondary winding of the hybrid coil H3 and, as dethe output-terminals 25.

lhe network N is designed so that there is no reflection ot the current passing into it, and its energy is entirely absorbed therein.

lt is designed to balance a network extendA ing,r to 'infinity whose sections are like those ot network D. The network D consists ot sections like the sections of his'. 2 except that there. are only half as many. The eurrent wave entering the network D from the lett traverses it to the right and is there reflected and goes back entering,Y the hybrid coil, as indicated by the arrow 26. lts energy is divided, partly going; out at the normal .inout terminals 24 and partly at'the 'normal output terminals 25.

lfihile there is no reflection between the hybrid coil and the network D" torcurreuts entering the network B at this place, there is complete reflection at the extreme unconnected end ot the network D, and thus it wiil be seen` that the network D is coin- 'pletely traversed twice, and since it has halt the number of sections ot' Fig. 2, the wave passes through the same number ot" sections as in Fig. 2.

Referring to Fig. 2, if there is an odd number of eondensers C and if the middle 'condenser is replaced by two condensers in parallel, as shown at 27, then it will be seen that if reflection can be accomplished at 27, the. completely reflected wave will have traversed the same number ot sections and will have been subjected to the Same moditying' influence asthe completely transmit- 'lhis is the prineiple of Fig. 3 as compared with Fig. 2'.

' llihile l have explained my invention in relation to a delay circuit, it will readily. be understood that its principle will be tound applicable. for the oase ot any'v circuit in which it is desired to make a change in the other reflecting the mouse? current at the output terminals as com,- pared with the current at the input terminals. A v

l elaini: y i. The method et educing a desired degree of change in electric wave currents bctween a paient input terminals and a. pair ot' output 'terminals which consists in sentiing the currents from the input terminals without immediate etlect on the output terminals through a. network that produces half the desired-change, and reflecting the currents backtlirough the said network to complete the desired change, making the reflected currents effective on the output terminals of the system.

2. ln combination, hybrid coil with out- ;out terminals unatl'ectcd directly by current introduced at the input terminals and a network to receive current from the input terminals and reflect ,it hack, the system being 'adayted to make the reflected current waves effective on the output terminals.

3. jln'combination, a hybrid coil with a pair o''t input terminais and a pair ot output terminals and with an absorbing network 'and a. retlectinsy :network balanced aeainst each other with respect one said pair ot terminals.

in combination, a hybrid coil 'with in- `put and output-terminals and two networks to which the input currents divide, one network being completely absorbent and the l waves transmitted through it whereby these waves, otter twice .traversing the last mentioned network, be-

come eii'ective 'on the output terminals.

n delay network comprising a, series- 'of sections andtwo conjugate pairs of ternnnals at one end'thereot, and means to establish the conyugate relation between Said nl la) lili.'

two pairs olx terminals whereby input currents on. one pair give an output on the other pair only by transmission through the said series ot sections and reflection back therethrough.

(i. The method of delayingvelectric wave currents in a network having two conjugate pairs of terminals4 which consists in applying the currents at one nair and delayingthem in transmission therethrough, then refleeting them back to cause further delay and putting them out at the' other pair ot terminals.

ln testimony whereof' l have signed my 'zname to this specification this :5th dayot September, N21i.

NYQUQST. 

